This invention relates to apparatus and method for calculating and displaying the location of an internal defect detected by nondestructive inspection techniques. More particularly, the invention relates to such apparatus and method in association with angled, ultrasonic inspection.
Nondestructive ultrasonic inspection techniques are commonly utilized in production situations for inspecting the internal portions of a specimen to locate potential defects therein. An example of use of such inspection techniques is for inspecting the internal quality of a weld joint, and a common technique for inspecting a weld joint includes utilization of angled, ultrasonic beam techniques. This inspection technique comprises utilization of an angled ultrasonic transducer which is capable of introducing an ultrasonic sound beam into the test specimen at a preselected angle relative thereto. The ultrasonic sound beam totally internally reflects within the material at opposing parallel surfaces thereof to travel within the material along a substantially sawtooth-configured path. The angle beam transducer acts not only as an ultrasonic sound wave source, but also as a microphone for detecting the echoed reflection of the sound beam when it encounters a defect in the test specimen, such as within the interior of the weld joint being inspected. The echoed reflection, of course, travels along the same sawtooth path back to the transducer and provides a signal, normally an electrical signal in the form of a display on a CRT tube, to give the operator information as to the total path length the sound wave traveled upon contacting the located defect. Upon detecting the defect, the operator also is provided with information as to the actual distance between the transducer and a reference point in the test specimen or the weld joint thereof. The operator is then faced with the problem of calculating the actual location of the detected defect relative to the weld joint area being inspected to provide meaningful information to production personnel.
Normally such calculation includes manual determination and display of the sawtooth path, taking into account the thickness of the material being inspected as well as the particular angle of introduction of the sound beam into the test specimen. After generating such a layout of the sawtooth path of the sound wave, the operator must then measure along the length of the sawtooth path to locate the point related to the readout received from the angled transducer as to the total distance the sound wave traveled prior to encountering the defect. After so determining the relative location of the defect the operator must then relate the location to the configuration of the weld joint to this determined location of the defect in order to determine the precise location of the detected defect relative to the weld joint area being inspected. Such prior art, relatively totally manual techniques are quite time-consuming and include continuous, repetitive calculations of the same nature tending to cause errors in the process. Accordingly, it will be apparent that it is relatively time-consuming and inaccurate to develop a separate, manual calculation and display for each detected defect taking into account the various parameters involved including the angle of the sound beam, the thickness of the test specimen, and the determination of which portion of the sawtooth curve the defect was detected upon.
Another prior art method of calculating a located defect includes an arrangement for determining the location of the detected defect relative to the thickness of the test specimen. However, this prior art arrangement, such as illustrated in "NONDESTRUCTIVE TESTING-ULTRASONIC TESTING", Classroom Training Handbook CT-6-4, General Dynamics, Convair Division, San Diego, Calif., Copyright 1967, pages 4-27 and 28, is usable only for one particular angle of sound beam introduction, has a limited capability with regard to accuracy and universality, and still requires the determination in a separate manner of the location of the defect within the weld area being inspected.
It is quite important in a production situation that the location of the defect relative to the weld joint being inspected be rapidly and accurately calculated. This provides information, for example, to reset a weld setup to eliminate the detected defect. More particularly, if the defect is located well within the interior of the weld joint this advises the weld operator that porosity has been detected. Specific information as to the location of such porosity will advise the operator on the best manner for readjusting the weld setup to eliminate the defect in subsequent welding operations. Similarly, if a defect is located in the joint area of the weld, this provides information that the defect is in the form of lack of fusion, telling the weld operator further information as to how to most rapidly eliminate the defect.